Poly (3-hexylthiophene) (P3HT) is a wide application in active layer of solar cell. It is a soluble conductive polymer but their mechanical properties are poor and its conductivity is unstable in environmental condition. We add polymethylmethacrylate (PMMA) into active layer to overcome these disadvantages. We investigated the effect of adding PMMA and graphene into solar cell on its characteristics of polymer solar cell. The cell structure was ITO/PEDOT:PSS/P3HT:PCBM:PMMA/Ca/Al. The 0.02, 0.04 and 0.06 weight ratio of PMMA were added into the P3HT:PCBM (1:1 ratio by weight) active layer. The device with 0.04 PMMA exhibits the highest short circuit current density (Jsc, 9.01 mA/cm2 ) and power conversion efficiency (PCE, 3.39%). The increases of Jsc and PCE are 26.5% and 49.3%, respectively compared with the device based on the pristine P3HT:PCBM active layer giving Jsc and PCE of 7.12 mA/cm2 and 2.27%. Graphene exhibits good electron conductivity, thermal conductivity, chemical stability and strength. We investigated the effect of inserting graphene between hole transfer layer (HTL) of poly (ethylene dioxythiophene) (PEDOT)-polystyrene sulfonic acid (PSS) (PEDOT:PSS) and active layer on the characteristics of polymer solar cell. The cell structure was ITO/PEDOT:PSS/Graphene/P3HT:PCBM:PMMA/Ca/Al. The concentration of graphene solution was 2.2 mg/ml and the graphene layer was coated by spin-coating at 6000 rpm and the weight ratio of PMMA in the P3HT:PCBM active layer was 0.04. The Jsc of device was increased to 9.45 mA/cm2 , an increase of 32.7%. The PCE of the device was increased to 3.63%, an increase of 59.9%.